The most important application of the above research is for assessing the predictability of climate variability on decadal time scales. Considerable progress has been made recently on the prediction of climate change related to the El Nino Southern Oscillation (about four year cycles) (see Battisti in this volume). Prediction of climate change on longer time scales would have obvious benefits for agriculture, those industries producing products used for heating/cooling, and for groundwater supplies. The negative effects of droughts could be ameliorated by, for example, rotation of crops and changing the time and place of agricultural planting. Long term climate changes can have a major effect on coastal regions through rising and falling sea level, and saltwater intrusions into groundwater aquifers. In addition, changes in oceanic circulation regimes affect fish stocks.
Besides natural changes in climate, in the last hundred years
the threat of anthropogenic effects on climate has increased. One
of these effects involves the addition to the atmosphere of large
amounts of excess CO
due to deforestation and burning of fossil
fuels. The ocean's have taken up a considerable portion of the
anthropogenic CO
released to the atmosphere. A large part of
the uptake occurs in high latitude regions as part of the process
of deep water mass formation. How rapidly these waters are carried
into the ocean's interior will have an effect on how rapidly
anthropogenic CO
is taken up. The transient tracer research
reviewed here is providing time scale estimates for these
circulation processes. A direct application of the time scale
information derived from tracers is to calculate fluxes of CO
into the oceans. Another application is to gain knowledge of the
spreading rate of other pollutants introduced into the oceans. For
deep sea burial of wastes, rates of bottom circulation and
upwelling into the overlying waters are needed. For example, if
the upwelling rate is high and the life-time of the material
disposed is long, then the material could mix upwards and cause
potential harm to the food chain.